This invention relates to a driving wheel slip control system for vehicles, and more particularly to a driving wheel control system for a vehicle in which is installed an internal combustion engine having a plurality of cylinders arranged in two banks, one located in a front portion of the engine room and the other in a rear portion of the same.
As recognized in general, a driving wheel of an automotive vehicle undergoes a slip when the vehicle is started to run or when it is accelerated, if the driving force of the driving wheel surpasses a frictional force developed between the tire of the driving wheel and the road surface.
In order to control or prevent such slips of driving wheels, driving wheel slip control (hereinafter referred to as "traction control") is conventionally carried out. According to the oonventional traction control, when an excessive slip of at least one driving wheel is detected, the output torque (driving force) of the engine is reduced to thereby suppress the excessive slip. The reduction of output torque of the engine can be performed very effectively by cylinder-by-cylinder control, e.g. by gradually increasing the number of cylinders to be subjected to fuel cut. For example, a driving wheel slip control system has been proposed by Japanese Provisional Patent Publication (Kokai) No. 58-8436, in which a slip state of at least one driving wheel is detected, and in response to the detected slip state, the supply of fuel to the engine connected to the driving wheels is cut off, cylinder by cylinder.
However, depending on the type of an internal combustion engine installed in the vehicle, fuel cut carried out in accordance with the traction control can cause increase in the temperatures of the engine per se, an exhaust gas concentration sensor arranged in the exhaust system, a catalyst for purifying exhaust gases, etc.
More specifically, in the case of a V-type engine disposed transversely of the engine room, a plurality of cylinders are arranged in two banks, one located in a front portion of the engine room (i.e. front bank) and the other in a rear portion of same (i.e. rear bank). Since part of the engine room on the rear side of the engine is hard to cool off, the heat of the rear bank of the cylinders cannot be efficiently dissipated, so that the temperature of the rear bank tends to be higher than that of the front bank. The higher temperature of the rear bank of the cylinders also results in inoreased temperature of the exhaust system of the rear bank, increasing the temperatures of the above-mentioned devices.
If in the above-mentioned type of engine in which the rear bank of the cylinders is higher in temperature than the front bank of same, cylinders are subjected to fuel cut in accordance with the traction control indiscriminately, i.e. irrespective of whether the cylinders to be subjected to fuel cut are on the front bank or the rear bank, when the conditions for carrying out fuel cut are satisfied, the temperatures of cylinders on the rear bank can become excessively high since cooling of the rear bank by fuel is not effected.
The thus increased temperature of the engine oan cause undesired thermal damage to the cylinder block of the engine as well as to the exhaust system. Therefore, there is room for improvement in the traction control of carrying out fuel cut of cylinders irrespective of whether cylinders are on the front bank or the rear bank by the driving wheel slip control system for the above-mentioned type of engine.